Semiconductor image sensors are used for sensing light. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as digital still camera or mobile phone camera applications. These devices utilize an array of pixels in a substrate, including photodiodes and transistors, that can absorb radiation projected towards the substrate and convert the sensed radiation into electrical signals. Thus, an image sensor's efficiency in sensing the projected radiation depends on how much radiation is absorbed by the pixels. However, image sensors fabricated using current technologies are not optimized for the absorption of radiation by the pixels. Thus, while existing methods of fabricating image sensors have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.